NAT configuration?

i am running Asterisk behind NAT, my SQUID is while the Asterisk server is running at, i have given following commands at squid

[code] iptables -t nat -A PREROUTING -i eth0 -d -p udp --dport 10000:20000 -j DNAT --to-destination

iptables -t nat -A PREROUTING -i eth0 -d -p udp --dport 5060 -j DNAT --to-destination[/code]

Same configuration is done at remote branch office SQUID.

and i have added following line in sip.conf


but when we try to call each other using xten SIP phone we get NO ROUTE TO HOST error?

please help me out,